1. Field of the Invention
The present invention relates to a semiconductor integrated circuit device, and in particular, to a semiconductor integrated circuit device comprising an electrically rewritable nonvolatile semiconductor storage device.
2. Description of the Related Art
Electrically rewritable nonvolatile semiconductor storage devices, for example, multivalue flash memories require a reduction in the breadth of distribution of a write threshold voltage.
However, a decrease in the breadth of distribution of the write threshold voltage requires a reduction in the shift in the threshold voltage during a write operation. This may slow down the write operation.
Document 1: Jpn. Pat. Appln. KOKAI Publication No. 2003-196988 (corresponding U.S. patent: U.S. Pat. No. 6,643,188)